Spring Boot Dependency Management

Spring Boot manages dependencies and configuration automatically. Each release of Spring Boot provides a list of dependencies that it supports. The list of dependencies is available as a part of the Bills of Materials (spring-boot-dependencies) that can be used with Maven. So, we need not to specify the version of the dependencies in our configuration. Spring Boot manages itself. Spring Boot upgrades all dependencies automatically in a consistent way when we update the Spring Boot version.

Advantages of Dependency Management

• It provides the centralization of dependency information by specifying the Spring Boot version in one place. It helps when we switch from one version to another.
• It avoids mismatch of different versions of Spring Boot libraries.
• We only need to write a library name with specifying the version. It is helpful in multi-module projects.

Note: Spring Boot also allows overriding of dependencies version, if required.

Maven Dependency Management System

The Maven project inherits the following features from spring-boot-starter-parent:

• The default Java compiler version
• UTF-8 source encoding
• It inherits a Dependency Section from the spring-boot-dependency-pom. It manages the version of common dependencies. It ignores the <version> tag for that dependencies.
• Dependencies, inherited from the spring-boot-dependencies POM
• Sensible resource filtering
• Sensible plugin configuration

Inheriting Starter Parent

The following spring-boot-starter-parent inherits automatically when we configure the project.

<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.2.2.BUILD-SNAPSHOT</version>      <!-- lookup parent from repository -->
<relativePath/> 
</parent>

Note: In the above dependency, we have specified only the Spring Boot version. If we want to add additional starters, simply remove the <version> tag. Similarly, we can also override the individual dependency by overriding a property in our project.

For example, if we want to add another dependency with the same artifact that we have injected already, inject that dependency again inside the <properties> tag to override the previous one.

Changing the Java version

We can also change the Java version by using the <java.version> tag.

<properties>  
<java.version>1.8</java.version>  
</properties>

Adding Spring Boot Maven Plugin

We can also add Maven plugin in our pom.xml file. It wraps the project into an executable jar file.

<build>  
<plugins>  
<plugin>  
<groupId>org.springframework.boot</groupId>  
<artifactId>spring-boot-maven-plugin</artifactId>  
</plugin>  
</plugins>  
</build>  

Spring Boot without Parent POM

If we don't want to use spring-boot starter-parent dependency, but still want to take the advantage of the dependency management, we can use <scope> tag, as follows:

Note: It does not maintain the plugin management.

<dependencyManagement>
<dependencies>
<dependency><!-- Import dependency management from Spring Boot -->
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-dependencies</artifactId>
<version>2.2.2.RELEASE</version>
<type>pom</type>
<scope>import</scope>
</dependency>
</dependencies>
</dependencyManagement>

The above dependency does not allow overriding. To achieve the overriding, we need to add an entry inside the <dependencyManagement> tag of our project before the spring-boot-dependencies entry.

For example, to upgrade another spring-data-releasetrain, add the following dependency in the pom.xml file.

<dependencyManagement>
<dependencies>
<!--Override Spring Data release train-->
<dependency>
<groupId>org.springframework.data</groupId>
<artifactId>spring-data-releasetrain</artifactId>
<version>Fowler-SR2</version>
<type>pom</type>
<scope>import</scope>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-dependencies</artifactId>
<version>2.2.2.RELEASE</version>
<type>pom</type>
<scope>import</scope>
</dependency>
</dependencies>
</dependencyManagement>